Pressing Machine, Pressing Method, and Punched Article

ABSTRACT

A press working apparatus is provided with a first working unit and a second working unit  14 . In the first working unit, a first stage is performed for forming a half-blanked portion  15  with a projecting shape at a region where a through hole P is to be formed in a sheet W. In the second working unit  14 , a second stage S 2  is performed in which the half-blanked portion  15  is blanked from the sheet W by a second punch  26  and a second die  23 . Also in the second stage S 2 , when a blanked body is blanked from the sheet W, shaving work is performed with respect to a side wall surface Pa on a region of the sheet W where the blanked body has been blanked.

TECHNICAL FIELD

The present invention relates to a press working apparatus that performsblanking work on a relatively thick sheet, which will serve, forexample, as the raw material for a press-formed part for an automatictransmission, an element of a belt for a continuously variabletransmission, or the like, and relates to a press working method and ablanked product manufactured by the press working apparatus.

BACKGROUND ART

An example of a conventional press working apparatus of the same type isthe press working apparatus proposed and described in Patent Document 1(a press die apparatus for perforation). Such a press working apparatus(hereinafter referred to as a “first conventional apparatus”) isequipped with two working units (first and second working units). Theworking units are respectively provided with a punch and a die. In thefirst working unit, the punch and the die are relatively moved, suchthat a region of a sheet to be formed with a through hole having apredetermined shape (e.g. a shape with a generally circular crosssection) is formed with a half-blanked portion having a shape thatprojects toward the die side. In other words, at a first stage in thefirst working unit, a region of the sheet to be formed with a throughhole has a concave portion on a side facing the punch, and also has ahalf-blanked portion with a convex portion formed on a side facing thedie.

Next in the second working unit, for cases where the half-blankedportion of the sheet is disposed between the punch and the die, thepunch is disposed so as to be opposite the concave portion (of thehalf-blanked portion) of the sheet and the die is disposed so as to beopposite the concave portion (of the half-blanked portion) of the sheet.Furthermore, the diameter of the punch of the second working unit isformed smaller than the diameter of the through hole. At a second stagein the second working unit, the punch thereof presses the half-blankedportion of the sheet toward the die side, whereby the half-blankedportion becomes a blanked body and is blanked from the sheet.Accordingly, a through hole with a shape corresponding to the blankedbody is formed in the sheet.

However, in cases where the half-blanked portion is blanked from thesheet to become a blanked body by the first conventional apparatus, amajority of a side wall surface (a blanked surface along the blankingdirection on a region where the blanked body is blanked from the sheet)of the through hole in the sheet, and a majority of a side wall surface(a blanked surface along the blanking direction) of the blanked bodyrespectively become rough cross sections. Therefore, if the respectiveblanked body and the sheet formed with the through hole are to be turnedinto blanked products, then all of the respective side wall surfaces,including such rough cross sections, should be made smooth. It is thusnecessary to further utilize a separate device (such as a polishingdevice) in order to polish the side wall surface of the through hole andthe side wall surface of the blanked body. Hence, in recent times, forcases where a blanked body is blanked from a sheet, apparatuses havebeen proposed that are capable of suppressing the formation of roughnesson a cross section of the side wall surface of the through hole in thesheet. An example of such an apparatus is the press working apparatus(hereinafter referred to as a “second conventional apparatus”) describedin Patent Document 2.

The second conventional apparatus is equipped with three working units(first, second, and third working units). The working units arerespectively provided with a punch and a die. In the first working unit,almost identical to the first working unit in the first conventionalapparatus, a half-blanked portion is formed at a region of a sheet whereblanking work is performed. In the second working unit, almost identicalto the second working unit in the first conventional apparatus, a hole(a blank hole) is formed in the sheet by blanking from the sheet ahalf-blanked portion, which becomes a blanked body. In this case, theblank hole is formed such that a diameter thereof is slightly smallerthan the diameter of the through hole to be ultimately formed in thesheet. In the third working unit, a punch whose diameter is almost thesame as the diameter of the through hole is pressed into a region to beformed with the through hole (a region surrounding the blank hole),whereby the punch performs shaving work on the side wall surface of theblank hole. As a consequence, the sheet becomes a blanked product formedwith a through hole that has a side wall surface with a sheared-surfaceshape.

Incidentally, in the second conventional apparatus, the three stages offorming a half-blanked portion in a sheet, forming a blank hole in thesheet, and performing shaving work on the side wall surface of the blankhole are performed in that order. Therefore, in actuality, the number ofprocesses needed to form a through hole shaped with a sheared-surfaceshape in a sheet is no different from a press working method that usesthe first conventional apparatus to perform the first stage and thesecond stage, and uses a separate device to additionally perform thethird stage (a polishing process). Moreover, the second conventionalapparatus has a further problem: the third working unit for performingshaving work on the side wall surface of the blank hole (the thirdstage) must be further provided, and therefore the apparatus structureincreases in size by a corresponding amount compared to the firstconventional apparatus.

Patent Document 1: Japanese Patent Application Publication No.JP-A-9-174492 (FIGS. 2 and 3)

Patent Document 2: Japanese Patent Application Publication No.Jp-A-2004-176853 (Claim 1, FIG. 1)

DISCLOSURE OF THE INVENTION

The present invention was devised in light of the foregoingcircumstances. It is an object of the present invention to provide apress working apparatus capable of forming into a sheared-surface shapeat least a portion of blanked surfaces along the blanking direction on aregion of a sheet from which a blanked body has been blanked and on theblanked body that has been blanked from the sheet, and capable ofsuppressing the generation of burrs on the sheet, while at the same timesuppressing an increase in the size of the apparatus and the number ofprocesses for performing blanking work on the sheet; and it is a furtherobject of the present invention to provide a press working method and ablanked product.

In order to achieve the above object, a press working apparatusaccording to the present invention is a press working apparatus, whichperforms blanking work on a sheet, that includes: a first working unithaving a first upper die and a first lower die, wherein at least one ofthe first upper die and the first lower die is mobile in the verticaldirection with respect to the other, with the first upper die fixedlyattached with at least one among an opposing first punch and a firstdie, and the first lower die fixedly attached with the other among thefirst punch and the first die, and a negative clearance is set betweenthe first punch and the first die as viewed from the downward direction,and half-blanking work is performed on the sheet by relatively movingthe first punch and the first die in the vertical direction; and asecond working unit having a second upper die and a second lower die,wherein at least one of the second upper die and the second lower die ismobile in the vertical direction with respect to the other, with thesecond upper die fixedly attached with at least one among a second punchand a second die having a paired relationship, and the second lower diefixedly attached with the other among the second punch and the seconddie, and a positive clearance is set between the second punch and thesecond die as viewed from the vertical direction, and when ahalf-blanked portion that was formed in the sheet by half-blanking workperformed by the first working unit is blanked to become a blanked bodyby the second punch, a blanked surface is formed along a blankingdirection on a region where the blanked body is blanked from the sheet,and at least a portion of the blanked surface is subjected to shavingwork performed by the second punch.

In the press working apparatus according to the present invention, thesecond punch is structured so as to achieve a form wherein across-sectional shape for the second punch when cut in a directionorthogonal to the vertical direction is a similar and enlarged versionof a cross-sectional shape for the first punch when cut in a directionorthogonal to the vertical direction.

In the press working apparatus according to the present invention, thesecond punch is structured such that if the cross-sectional shape forthe second punch when cut in a direction orthogonal to the verticaldirection overlaps in the vertical direction with the cross-sectionalshape for the first punch when cut in a direction orthogonal to thevertical direction, then there is a distance dimension of 0.01 mm to 0.3mm between adjacent outer peripheral regions with mutually similarshapes.

In the press working apparatus according to the present invention, thefirst die is formed with a through hole running therethrough thatextends in the vertical direction, and the second punch is structuredsuch that the cross-sectional shape for the second punch when cut in adirection orthogonal to the vertical direction is a similar and enlargedshape of a hole shape of the through hole when the first die when is cutin a direction orthogonal to the vertical direction.

In the press working apparatus according to the present invention, thesecond punch is structured such that if the cross-sectional shape forthe second punch when cut in a direction orthogonal to the verticaldirection overlaps in the vertical direction with the cross-sectionalshape for the first die when cut in a direction orthogonal to thevertical direction, then there is a distance dimension of 0.01 mm to 0.3mm between an outer peripheral region of the cross section of the secondpunch and an inner peripheral region of the cross section of the firstdie, which have a mutually similar relationship.

The press working apparatus according to the present invention is apress working apparatus, which performs blanking work on a sheet, thatincludes: a first working unit having a first upper die and a firstlower die, wherein at least one of the first upper die and the firstlower die is mobile in the vertical direction with respect to the other,with the first upper die fixedly attached with at least one among anopposing first punch and a first die, and the first lower die fixedlyattached with the other among the first punch and the first die, and anegative clearance is set between the first punch and the first die asviewed from the vertical direction, and half-blanking work is performedon the sheet by relatively moving the first punch and the first die inthe vertical direction; and a second working unit having a second upperdie and a second lower die, wherein at least one of the second upper dieand the second lower die is mobile in the vertical direction withrespect to the other, with the second upper die fixedly attached with atleast one among a second punch and a second die having a pairedrelationship, and the second lower die fixedly attached with the otheramong the second punch and the second die, and a positive clearance isset between the second punch and the second die as viewed from thevertical direction, and when a half-blanked portion that was formed inthe sheet by half-blanking work performed by the first working unit isblanked to become a blanked body by the second punch, a blanked surfaceis formed along a blanking direction on the blanked body, and at least aportion of the blanked surface is subjected to shaving work performed bythe second die.

In the press working apparatus according to the present invention, thefirst die and the second die are respectively formed with insertionholes running therethrough in the vertical direction, and the second dieis structured so as to achieve a form wherein a hole shape of theinsertion hole when the second die is cut in a direction orthogonal tothe vertical direction is a similar and scaled-down version of a holeshape of the insertion hole when the first die is cut in a directionorthogonal to the vertical direction.

In the press working apparatus according to the present invention, thesecond die is structured such that if a cross-sectional shape for thesecond die when cut in a direction orthogonal to the vertical directionoverlaps in the vertical direction with a cross-sectional shape for thefirst die when cut in a direction orthogonal to the vertical direction,then there is a distance dimension of 0.01 mm to 0.3 mm between an outerperipheral region of a cross section of the second die and an innerperipheral region of a cross section of the first die, which have amutually similar relationship.

In the press working apparatus according to the present invention, thefirst working unit is structured such that if the first punch is made torelatively approach the first die, then the first punch is made toapproach up to a position that is separated only by a distance dimensionthat is 10% to 50% of a thickness dimension of the sheet.

In the press working apparatus according to the present invention, thefirst punch is formed such that a width dimension of the negativeclearance is a width dimension that is 1% to 15% of the thicknessdimension of the sheet.

In the press working apparatus according to the present invention, thesecond punch is fixedly attached with the second lower die if the firstpunch is fixedly attached with the first upper die, and the second punchis fixedly attached with the second upper die if the first punch isfixedly attached with the first lower die.

In the press working apparatus according to the present invention, thesecond punch is formed such that a width dimension of the positiveclearance is a width dimension that is 0.3% to 8% of the thicknessdimension of the sheet.

In the press working apparatus according to the present invention, atleast one among an end edge portion on a side facing the sheet in thefirst punch and an inner-side edge portion on a side facing the sheet inthe first die is subjected to chamfering work so as to have a curvedsurface.

In the press working apparatus according to the present invention, thecurved surface formed on at least one among the end edge portion on aside facing the sheet in the first punch and the inner-side edge portionon a side facing the sheet in the first die is formed so as to achievean arc shape, which has a curvature radius with a length dimension thatis equal to or less than 7.5% of the thickness dimension of the sheetwhen the first punch and the first die are cut in the verticaldirection.

In the press working apparatus according to the present invention, anend edge portion on a side facing the sheet in the second punch issubjected to chamfering work so as to have a curved surface.

In the press working apparatus according to the present invention, thecurved surface of the end edge portion on a side facing the sheet in thesecond punch is formed so as to achieve an arc shape, which has acurvature radius with a length dimension that is equal to or less than7.5% of the thickness dimension of the sheet when the second punch iscut in the vertical direction.

A blanked product according to the present invention is manufactured byblanking a blanked body from a sheet using a press working apparatus asstructured above.

A press working method according to the present invention is a pressworking method, which performs blanking work on a sheet, that includes:a first stage where a first punch and a first die in a pairedrelationship are used to perform half-blanking work on a region where ablanked body is to be blanked in the sheet; and a second stage where asecond punch and a second die in a paired relationship are used to blankthe blanked body from the region in the sheet subjected to half-blankingin the first stage, and at such time, the second punch performs shavingwork on at least a portion of a blanked surface along a blankingdirection on a region where the blanked body is blanked.

A press working method according to the present invention is a pressworking method, which performs blanking work on a sheet, that includes:a first stage where a first punch and a first die in a pairedrelationship are used to perform half-blanking work on a region where ablanked body is to be blanked in the sheet; and a second stage where asecond punch and a second die in a paired relationship are used to blankthe blanked body from the region in the sheet subjected to half-blankingin the first stage, and at such time, the second die performs shavingwork on at least a portion of a blanked surface along a blankingdirection on the blanked body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic front view of a press working apparatus according toa first embodiment.

FIG. 2 is a schematic cross-sectional view showing a portion of a firstworking unit according to the first embodiment.

FIG. 3 is a schematic cross-sectional view showing how a first punchcontacts a sheet in the first working unit.

FIG. 4 is a schematic cross-sectional view showing how the first workingunit performs half-blanking work on the sheet.

FIG. 5 is a schematic cross-sectional view showing the first punch atits closest approach to a first die in the first working unit.

FIG. 6 is a schematic cross-sectional view showing a portion of a secondworking unit according to the first embodiment.

FIG. 7 is a schematic cross-sectional view showing the start of a strokemovement of a second punch toward a second die side in the secondworking unit.

FIG. 8 is a schematic cross-sectional view showing the second punchpress a half-blanked portion of the sheet in the second working unit.

FIG. 9 is a schematic cross-sectional view showing the start of shavingwork in the second working unit on a region to serve as a side wallsurface of a through hole.

FIG. 10 is a schematic cross-sectional view showing the performance ofshaving work in the second working unit on the region to serve as theside wall surface of the through hole.

FIG. 11 is a schematic cross-sectional view showing the blanked bodybeing blanked from the sheet in the second working unit.

FIG. 12 is a schematic cross-sectional view showing the end of a secondstage in the second working unit.

FIG. 13 is a schematic cross-sectional view showing a portion of thefirst working unit according to a second embodiment.

FIG. 14 is a schematic cross-sectional view showing a portion of thesecond working unit according to the second embodiment.

FIG. 15 is a schematic cross-sectional view showing the start of astroke movement of the second punch toward the second die side in thesecond working unit.

FIG. 16 is a schematic cross-sectional view showing the second punchpress the half-blanked portion of the sheet in the second working unit.

FIG. 17 is a schematic cross-sectional view showing the start of shavingwork in the second working unit on a region to serve as the side wallsurface of the blanked body.

FIG. 18 is a schematic cross-sectional view showing the performance ofshaving work in the second working unit on the region to serve as theside wall surface of the blanked body.

FIG. 19 is a schematic cross-sectional view showing the blanked bodybeing blanked from the sheet in the second working unit.

FIG. 20 is a schematic cross-sectional view showing the blanked bodybeing blanked from the sheet in the second working unit according to athird embodiment.

FIG. 21 is a view showing a frame format of another example of a crosssectional-shape of the first punch and a cross-sectional shape of thesecond punch overlapped.

FIG. 22 is a plane view of a carrier formed by further processing thesheet press worked by the press working apparatus according to the firstembodiment.

FIG. 23 is a cross-sectional arrow view taken along a line 23-23 in FIG.23.

FIG. 24 is a plane view of a backing plate formed by processing thesheet press subsequent to press working by the press working apparatusaccording to the second embodiment.

FIG. 25A is a schematic cross-sectional view showing the performance ofhalf-blanking work on a region formed with a notch portion on the sheet;FIG. 25B is a schematic cross-sectional view showing the notch portionformed on the sheet; and FIG. 25C is a schematic plane view showing thenotch portion formed on the sheet.

BEST MODES FOR CARRYING OUT THE INVENTION First Embodiment

Hereinafter, with reference to FIGS. 1 to 12, a first embodiment will beexplained that realizes the present invention as a press workingapparatus and a press working method which are used when a blanked bodyis blanked from a relatively thick sheet.

As FIG. 1 shows, a press working apparatus 11 according to the presentembodiment has a first working unit 13 and a second working unit 14provided in parallel on a base plate 12. Using the respective workingunits 13, 14, the press working apparatus 11 is designed to form athrough hole P (see FIG. 12) with a predetermined shape (whose crosssection is a generally circular shape in the present embodiment) in asheet W, which is formed from a metallic material (e.g. hot-rolled sheetsteel (JIS SPH440) for automobile structures). Namely, in the firstworking unit 13, as FIG. 5 shows, a region where the through hole P isto be formed is half-blanked on the sheet W, and a half-blanked portion15 is formed having a shape that projects upward from the sheet W. Inthe second working unit 14, as FIG. 12 shows, the half-blanked portion15 formed by the first working unit 13 is blanked and becomes a blankedbody 15A (see FIG. 11). The through hole P is thus formed at the regionwhere the blanked body 15A was blanked in the sheet W. At this time, thethrough hole P is subjected to shearing work (shaving work) such that aside wall surface (a blanked surface along the blanking direction) Pathereof becomes a sheared surface instead of a rough fracture surface.Thereafter, the sheet W from which the blanked body 15A was blanked isfurther worked, and as a result, a blanked product is formed. Note that“half-blanking work” refers to the time when a blanked body (the blankedbody 15A) is to be blanked from the sheet W. Such blanking is stoppedpartway so as to form a projection portion (the half-blanked portion 15)having a projecting shape in the sheet W.

Next, the first working unit 13 will be explained below based on FIGS. 1to 5.

As FIG. 1 shows, in the first working unit 13, a lower die (a firstlower die) 16 is disposed on the base plate 12, and a first punch 17 isfixedly attached on the lower die 16. Furthermore, a plurality (four)cylindrical columns 18 are arranged in a standing condition on the baseplate 12 so as to extend in the vertical direction and run through thefour corners of the lower die 16. The lower die 16 is designed to moveup and down along the respective columns 18. Although not shown in thefigure, the first working unit 13 is also provided with a driving source(e.g. an actuator formed from a hydraulic cylinder (a fluid pressurecylinder) and the like) for the purpose of moving the lower die 16 (andthe first punch 17) between the bottom dead center position and the topdead center position in strokes.

Additionally, in the first working unit 13, an upper die (a first upperdie) 19 is supported in an area over the lower die 16 by the respectivecolumns 18, and a first die 20 that corresponds to the first punch 17 isfixedly attached to a lower surface side of the upper die 19.Furthermore, the first working unit 13 is provided with a sheet pushingportion (not shown) that pushes the sheet W upward, such that when thesheet W is carried into the first working unit 13 and subjected to pressworking, an upper surface Wa of the sheet W comes in contact with alower surface 20 a of the first die 20. The first die 20, as FIG. 2shows, is formed with a first die hole (insertion hole) 21 thatcorresponds to a cross-sectional shape (a hole shape) of the throughhole P and has a cross section with a generally circular shape. Thefirst die hole 21 has a diameter dimension D1 (e.g. 29.9 mm) that is setso as to be slightly smaller than a diameter dimension d1 of the throughhole P. Note that in the present embodiment, an inner-side edge portion20 b on the lower surface 20 a side (a side facing the sheet W) of thefirst die 20 is not subjected to processing that would form a curvedsurface with a certain radius.

The first punch 17 is formed so as to have a generally cylindrical shapecorresponding to the cross-sectional shape (the hole shape) of thethrough hole P. An end edge portion 17 b on an upper surface 17 a side(a side facing the sheet W) of the first punch 17 is subjected toprocessing so as to have a curved surface 17 c with a certain radius.Therefore, by facing the first punch 17 upward and moving it, the sheetW is subjected to half-blanking work. In such case, as FIG. 5 shows, ona lower surface Wb side of the sheet W, a deformation Wc is formed whoseshape has a curved surface. The curved surface 17 c of the end edgeportion 17 b of the first punch 17 according to the present embodimentis formed into an arc shape whose curvature radius has a lengthdimension (e.g. 0.2 mm) that is 5% of a thickness dimension d (e.g. 4mm) of the sheet W.

In addition, the first punch 17, as can also be understood from FIG. 2,has a diameter dimension D2 (e.g. 30.1 mm) that is set so as to begreater than the diameter dimension D1 of the first die hole (insertionhole) 21 of the first die 20. In other words, the first punch 17 and thefirst die 20 (the first die hole 21) are in a mutually correspondingrelationship, and a clearance (a width dimension of the clearance) C1therebetween is set so as to be a negative clearance (C1=(D1−D2)/2<0).In the present embodiment, the first punch 17 is formed such that theclearance C1 has a width dimension (e.g. 0.1 mm) that is 2.5% of thethickness dimension d (e.g. 4 mm) of the sheet W. Accordingly, the firstpunch 17 of the present embodiment is set such that the differencebetween the diameter dimension D2 of the first punch 17 and the diameterdimension D1 of the first die hole 21 is double the clearance C1 (i.e.,D1−D2=2×C1).

Note that the “clearance” refers to a gap created between the punch (thefirst punch 17) and the die hole (the first die hole 21) when viewedfrom the vertical direction. If the clearance (the clearance C1) is a“negative clearance”, this indicates that the diameter (the diameterdimension D2) of the punch (the first punch 17) is greater than thediameter (the diameter dimension D1) of the die hole (the first die hole21). Namely, the “forming a negative clearance” refers to the punchoverlapping on a region of the die around the die hole as viewed fromthe vertical direction, and does not mean that a gap is actually createdbetween the punch and the die hole as viewed form the verticaldirection. On the other hand, if the clearance is a “positiveclearance”, this indicates that the diameter of the punch is smallerthan the diameter of the die hole.

Next, a first stage S1 performed by the first working unit 13 will beexplained below.

A region to be blanked (a region where the through hole P is formed) onthe sheet W is disposed in an area over the first punch 17. At suchtime, the sheet pushing portion pushes the sheet W upward (toward thefirst die 20 side), and puts the upper surface Wa of the sheet W incontact with the lower surface 20 a of the first die 20. Next, the firstpunch 17 moves upward from the bottom dead center position in a strokeaccording to driving of the hydraulic cylinder. Thus, as FIG. 3 shows,the upper surface (an opposite surface facing the sheet W) 17 a of thefirst punch 17 contacts the lower surface Wb of the sheet W, and such acontacted region is pressed upward by the first punch 17. As aconsequence, the sheet W, as FIG. 4 shows, is formed with a half-blankedportion 15, which has a shape that projects toward the first die 20 side(upward). Accordingly, in the first working unit 13, the first punch 17and the first die 20 are relatively moved in the vertical direction,whereby a region to be blanked in the sheet W is subjected tohalf-blanking work.

Here, as mentioned earlier, the clearance C1 between the first punch 17and the first die 20 (the first die hole 21) is a negative clearance.However, in the present embodiment, the end edge portion 17 b of thefirst punch 17 is processed so as to have an arc shape. Therefore, thepressing force applied to the first punch 17 when the first punch 17pushing the sheet W toward the first die 20 becomes smaller compared towhen the end edge portion 17 b of the first punch 17 is not processed.In other words, the load applied to the first punch 17 (especially theload applied to the blade edge) is satisfactorily reduced.

Subsequently, as FIG. 5 shows, the first punch 17 moves in a stroke upto the top dead center position, and movement further upward is stopped.At this time, the upper surface 17 a of the first punch 17 approachesthe lower surface 20 a of the first die 20 up to a position separated bya distance dimension d2, which is 35% of the thickness dimension d ofthe sheet W. Next, the first punch 17 moves to the bottom dead centerposition (see FIG. 2), after which movement is stopped. In other words,the first stage S1 in the first working unit 13 ends. Thereafter,pushing up of the sheet W by the sheet pushing portion is stopped, andthe sheet W moves away from the first die 20. The sheet W issubsequently passed from the first working unit 13 into the secondworking unit 14. Note that a region contacting the end edge portion 17 bof the first punch 17 during the stroke movement up to the top deadcenter position (called a “first side wall surface 15 sh of thehalf-blanked portion 15”) is shaved by the first die 20, and thereforeformed into a sheared-surface shape.

Next, the second working unit 14 will be explained below based on FIG. 1and FIGS. 6 to 12.

As FIG. 1 shows, in the second working unit 14, a lower die (a secondlower die) 22 is disposed on the base plate 12, and a second die 23 isfixed attached on the lower die 22. The second die 23, as FIG. 6 shows,is formed with a second die hole (insertion hole) 24 that corresponds tothe cross-sectional shape (the hole shape) of the through hole P and hasa cross section with a generally circular shape. The second die hole 24has a diameter dimension D4 (e.g. 30.9 mm) that is set so as to beslightly greater than the diameter dimension d1 of the through hole P.Furthermore, the cylindrical columns 18 are arranged in a standingcondition at the four corners of the lower die 22. An upper die (asecond upper die) 25 is supported vertically mobile in an area over thelower die 22 by the columns 18. Although not shown in the figure, thesecond working unit 14 is also provided with a driving source (e.g. anactuator formed from a hydraulic cylinder (a fluid pressure cylinder)and the like) for the purpose of moving the upper die 25 (and a secondpunch 26) between the bottom dead center position and the top deadcenter position in strokes. Note that the driving source is provided ina manner similar to that of the first working unit 13.

A second punch 26 that has a paired relationship with the second die 23is fixedly attached to the lower surface side of the upper die 25.Namely, in the press working apparatus 11 according to the presentembodiment, the first punch 17 is fixedly attached to the lower die 16in the first working unit 13, and therefore, the second punch 26 isfixedly attached to the upper die 25 in the second working unit 14.Furthermore, the second punch 26 is formed in a generally cylindricalshape that corresponds to the cross-sectional shape (the hole shape) ofthe through hole P. The second punch 26 has a diameter dimension D3(e.g. 30.7 mm) that is set so as to be greater than the diameterdimension D2 of the first punch 17 by 0.6 mm, for example. In otherwords, the second punch 26 is structured so as to achieve a form whereinthe cross-sectional shape for the second punch 26 when cut in adirection orthogonal to the vertical direction is a similar and enlargedversion of the cross-sectional shape for the first punch 17 when cut ina direction orthogonal to the vertical direction. In addition, if thecross-sectional shape for the second punch 26 when cut in a directionorthogonal to the vertical direction overlaps in the vertical directionwith the cross-sectional shape for the first punch 17 when cut in adirection orthogonal to the vertical direction, then there is a distancedimension of, for example, 0.3 mm, between adjacent outer peripheralregions with mutually similar shapes. Note that the diameter dimensionD3 of the second punch 26 is set so as to enable the second punch 26 tocut (or shave in the present embodiment) a region of the sheet W onwhich the deformation Wc is formed.

In addition, the diameter dimension D3 of the second punch 26, as canalso be understood from FIG. 6, is set so as to be smaller than thediameter dimension D4 of the second die hole 24 in the second die 23,and substantially the same dimension as the diameter dimension d1 of thethrough hole P. In other words, the second punch 26 and the second die23 have a paired relationship, and a clearance (a width dimension of theclearance) C2 therebetween is set so as to be a positive clearance(C2=(D4−D3)/2>0). In the present embodiment, the second die 23 is formedsuch that the clearance C2 has a width dimension (e.g. 0.1 mm) that is2.5% of the thickness dimension d (e.g. 4 mm) of the sheet W. Note thatin the present embodiment, an end edge portion 26 b on a lower surface26 a side (a side facing the sheet W) of the second punch 26 is notsubjected to processing that would form a curved surface with a certainradius.

Next, a second stage S2 performed by the second working unit 14 will beexplained below.

The sheet W on which the first working unit 13 formed the half-blankedportion 15 is passed into the second working unit 14, and thehalf-blanked portion 15 is disposed below the second punch 26. Followingthis, the second stage S2 is started. In other words, the second punch26, as FIG. 7 shows, moves in a downward stroke toward the sheet W (thehalf-blanked portion 15), and presses the half-blanked portion 15 of thesheet W downward. Accordingly, a lower end side region (hereinafterreferred to as a “second side wall surface 15 sb of the half-blankedportion 15”) is formed into a fracture-surface shape at a connectingregion between the half-blanked portion 15 and the sheet W. As thesecond punch 26 presses the half-blanked portion 15 further downward, asFIG. 8 shows, the first side wall surface 15 sh and the second side wallsurface 15 sb of the half-blanked portion 15 connect, and result in thecutting of the half-blanked portion 15 from the sheet W.

Next, as FIG. 9 shows, the second punch 26 presses the half-blankedportion 15 further downward and starts to shear the sheet W. In otherwords, the second punch 26 blanks the half-blanked portion 15 from thesheet W and also starts to perform shaving work on a side wall surfacePa of the through hole P by blanking the half-blanked portion 15. AsFIG. 10 shows, further movement of the second punch 26 in the downwardstroke results in the progressive performance of shaving work on theside wall surface Pa of the through hole P.

At this point in time, the half-blanked portion 15 is still in a fittedstate inside the through hole P of the sheet W. However, with thefurther performance of shaving work on the side wall surface Pa by thesecond punch 26, as FIG. 11 shows, the half-blanked portion 15 is pushedout of the through hole P by the second punch 26 and becomes the blankedbody 15A. Note that scraps (shaving scraps) generated due to the secondpunch 26 performing shaving work on the side wall surface Pa adhere tothe blanked body 15A. Therefore, the side wall surface 15 a is formedinto a fracture-surface shape.

Here, the deformation Wc still remains on the lower surface Wb side ofthe sheet W. Thus, even if the lower surface 26 a of the second punch 26does not move further to the lower side than the upper surface 23 a ofthe second die 23, the blanked body 15A is still blanked from the sheetW. Thereafter, the downward stroke movement of the second punch 26 isstopped and an upward stroke movement is subsequently started, wherebythe blanking of the blanked body 15 a from the sheet W is completed. Theside wall surface Pa of the through hole P, as FIG. 12 shows, issubjected to shaving work by the second punch 26 and thus formed into asheared-surface shape.

In view of the above, the effects specified below can be obtained in thepresent embodiment.

(1) If, for instance, the clearance C1 between the first punch 17 andthe first die 20 (the first die hole 21) is set as a positive clearance,then tensile stress acts on a portion of the sheet W sandwiched betweenthe first punch 17 and the second die 20. Therefore, when the firstpunch 17 pushes the sheet W upward in the first working unit 13, thepushed region may fracture and form a fracture surface on the sheet W.However, in the present embodiment, the clearance C1 is a negativeclearance, and therefore compression stress acting on the portion of thesheet W sandwiched between the first punch 17 and the second die 20suppresses fractures. As a consequence, it is possible to suppress theformation of a fracture surface on the sheet W in the first working unit13. Furthermore, in the second working unit 14, the second punch 26performs shaving work on the side wall surface Pa of the through hole P,which is formed when the half-blanked portion 15 is blanked from thesheet W to become the blanked body 15A. Moreover, since the clearance C2between the second punch 26 and the second die 23 is a positiveclearance, it is possible to avoid contact between the second punch 26and the second die 23. Accordingly, an increase in the size of theapparatus itself and an increase in the number of processes forperforming blanking work on the sheet W can be suppressed. And at thesame time, it is possible to form into a sheared-surface shape the sidewall surface Pa of the through hole P that is formed in the sheet W, andalso possible to suppress the generation of burrs on the sheet W.

(2) In the first working unit 13, the half-blanked portion 15 is formedat a region where the through hole P is to be formed (a region to beblanked) in the sheet W; and in the second working unit 14, theperiphery of the half-blanked portion 15 is subjected to blanking work.Therefore, shaving scraps generated when the side wall surface Pa of thethrough hole P is subjected to shaving work in the second working unit14 can fall along with the half-blanked portion 15 as the blanked body15A, which is not used as a product. Moreover, adhering of the shavingscraps to the second punch 26 can be suppressed.

(3) In the first stage S1, if, for instance, the distance dimension d2between the upper surface 17 a of the first punch 17 and the lowersurface 20 a of the first die 20 is set to a distance dimension that isless than 10% of the thickness dimension d of the sheet W, then aproblem such as the following may occur. Namely, in this case, there isa possibility that the half-blanked portion 15 may be severed from thesheet W when half-blanking work is performed on the sheet W by movingthe first punch 17 in a stroke. On the other hand, if, for instance, thedistance dimension d2 is set to a distance dimension that is greaterthan 50% of the thickness dimension d of the sheet W, then a problemsuch as the following may occur. Namely, in this case, the thickness ofthe connecting region between the sheet W and the half-blanked portion15 is greater than that in the present embodiment. As a consequence,regardless of whether the second punch 26 presses the half-blankedportion 15 of the sheet W downward in the second stage S2, an increasedload acts on the second punch 26 at the times of blanking thehalf-blanked portion 15 and performing shaving work on the side wallsurface Pa of the through hole P. However, in the present embodiment,the distance dimension d2 is set to 35% of the thickness dimension d ofthe sheet W. Therefore, severing of the half-blanked portion 15 from thesheet W in the first stage S1 can be suppressed, and the load on thesecond punch 26 in the second stage S2 can be satisfactorily reduced.

(4) If, for instance, the clearance (the width dimension of the negativeclearance) C1 is set to a width dimension that is less than 1% of thethickness dimension d of the sheet W, then there is a possibility thatthe deformation Wc formed on the lower surface Wb side of the sheet inthe first stage S1 may become excessively large. In other words, whenthe half-blanked portion 15 is blanked from the sheet W in the secondstage S2, there is a risk that a portion of the deformation Wc mayremain on the sheet W. On the other hand, if the clearance C1 is set toa width dimension that is greater than 15% of the thickness dimension dof the sheet W, then when the first punch 17 pushes the sheet W upward,a load generated by such pushing increases the load on the first punch17 and the first die 20. Consequently, there is a risk of shortening thelives of the first punch 17 and the first die 20. However, in thepresent embodiment, the clearance C1 is set to a width dimension that is2.5% of the thickness dimension d of the sheet W. Therefore, the livesof the first punch 17 and the first die 20 can be satisfactorilylengthened. In addition, when the blanked body 15A is blanked from thesheet W in the second stage S2, the remaining of a portion of thedeformation Wc on the sheet W can be suppressed.

(5) When the first punch 17 presses the sheet W upward from below in thefirst working unit 13, the sheet W centered around the half-blankedportion 15 may rebound toward the upward side. However, in the secondworking unit 14, the second punch 26 blanks (presses) the half-blankedportion 15 from the sheet W downward from above. Therefore, warping ofthe sheet W generated while blanking work is performed in the firstworking unit 13 can be satisfactorily corrected.

(6) If, for instance, the clearance (the width dimension of the positiveclearance) C2 is set to a width dimension that is less than 0.3% of thethickness dimension d of the sheet W, then there is the risk of anincreased load acting on the second punch 26 and the second die 23 whenthe half-blanked portion 15 is blanked from the sheet W by the secondpunch 26. In other words, there is a possibility of shortening the livesof the second punch 26 and the second die 23. On the other hand, if theclearance C2 is set to a width dimension that is greater than 8% of thethickness dimension d of the sheet W, then when the second punch 26performs blanking work on the sheet W, burrs may be generated on thesheet W. However, in the present embodiment, the clearance C2 is set toa width dimension that is 2.5% of the thickness dimension d of the sheetW. Accordingly, the lives of the second punch 26 and the second die 23can be lengthened, and the generation of burrs on the sheet W when theblanked body 15A is blanked from the sheet W by the second punch 26 canbe satisfactorily suppressed.

(7) If, for instance, the difference between the diameter dimension D3of the second punch 26 and the diameter dimension D2 of the first punch17 is set shorter than 0.02 mm, then a problem such as the following mayoccur. Namely, the width dimension of the connecting region thatconnects the half-blanked portion 15 and the sheet W becomes excessivelyshort (the width of a certain shaving amount becomes excessively narrow)compared to that in the present embodiment. Therefore, there is a riskthat performing shaving work on the side wall surface Pa of the throughhole P will become difficult in the second stage S2. On the other hand,if, for instance, the difference between the diameter dimension D3 ofthe second punch 26 and the diameter dimension D2 of the first punch 17is set to longer than 0.6 mm, then a problem such as the following mayoccur. Namely, when the second punch 26 blanks the blanked body 15A fromthe sheet W in the second stage S2, the end edge portion 26 b of thesecond punch 26 shears a region that is separated from the half-blankedportion 15 formed in the first stage S1, whereby the load acting on thesecond punch 26 increases compared to that in the case of the presentembodiment. However, in the present embodiment, the second punch 26 isformed such that the difference between the diameter dimension D3thereof and the diameter dimension D2 of the first punch 17 is 0.6 mm.Therefore, the width of a certain shaving amount in the second stage S2can be satisfactorily ensured, and the life of the second punch 26 canbe further lengthened.

(8) The end edge portion 17 b of the first punch 17 is subjected tochamfering work so as to have an arc shape. Therefore, when the firstpunch 17 moves above the sheet W (toward the first die 20 side) in astroke, the load acting on the first punch 17 can be satisfactorilyreduced. Furthermore, the first punch 17 is also subjected to chamferingwork so as to have an arc shape, and thus formed to have a certain bluntblade configuration. Therefore, in the first stage S1, the severing of aregion pressed by the first punch 17 in the sheet W can be suppressed.

(9) If, for instance, when the first punch 17 is cut in the verticaldirection, the curved Surface 17 c of the end edge portion 17 b of thefirst punch 17 is formed into an arc shape whose curvature radius isgreater than a curvature radius with a length dimension that is 7.5% ofthe thickness dimension d of the sheet W, then a problem such as thefollowing may occur. Namely, when the sheet W is subjected to blankingwork in the first stage S1, there is a risk of forming an excessivelylarge deformation Wc on the sheet W. However, in the present embodiment,the curved surface 17 c of the end edge portion 17 b of the first punch17 is formed so as to have a curvature radius that is 5% of thethickness dimension d of the sheet W. Therefore, the deformation Wcformed on the sheet W can be satisfactorily suppressed so as not tobecome excessively large.

Second Embodiment

Next, a second embodiment according to the present invention will beexplained based on FIGS. 13 to 19. Note that the second embodimentdiffers somewhat from the first embodiment with respect to the workingunits. Thus, the following explanation will mainly describe portionsdiffering from the first embodiment; like symbols are used for membersand structures that are identical to or correspond to those in the firstembodiment, and redundant explanations shall be omitted.

The press working apparatus 11 according to the present embodiment hasthe first working unit 13 and the second working unit 14. In the firstworking unit 13, the first punch 17 is fixedly attached on the lower die16, and the first die 20 corresponding to the first punch 17 is fixedlyattached to the lower surface side of the upper die 19. The first punch17 is formed into a generally cylindrical shape, and also formed suchthat the diameter dimension D2 thereof is 30 mm, for example.

In addition, the first die 20, as FIG. 13 shows, is formed with thefirst die hole 21 that has a cross section with a generally circularshape. The negative clearance C1 between the first die 20 and the firstpunch 17 is set so as to have a width dimension (e.g. 0.15 mm) that is3.8% of the thickness dimension d (e.g. 4 mm) of the sheet W. Namely,the first die hole 21 of the first die 20 is set such that the diameterdimension D1 thereof is 29.7 mm, for example. Furthermore, theinner-side edge portion 20 b on the lower surface 20 a side (a sidefacing the sheet W) of the first die 20 is subjected to processing so asto have a curved surface 20 c with a certain radius. In the presentembodiment, when the first die 20 is cut in the vertical direction, thecurved surface 20 c of the inner-side edge portion 20 b of the first die20 is formed so as to have an arc shape whose curvature radius has alength dimension (e.g. 0.3 mm) that is 7.5% of the thickness dimension d(e.g. 4 mm) of the sheet W.

Next, the first stage S1 performed by the first working unit 13 will beexplained below.

A region to be blanked on the sheet W is disposed in an area over thefirst punch 17. At such time, the sheet pushing portion pushes the sheetW upward (toward the first die 20 side), and puts the upper surface Waof the sheet W in contact with the lower surface 20 a of the first die20. Next, the first punch 17 moves upward from the bottom dead centerposition in a stroke according to driving of the hydraulic cylinder.Thus, the upper surface (an opposite surface facing the sheet W) 17 a ofthe first punch 17 contacts the lower surface Wb of the sheet W, andsuch a contacted region is pressed upward by the first punch 17. As aconsequence, the sheet W is formed with the half-blanked portion 15,which has a shape that projects toward the first die 20 side (upward).Accordingly, in the first working unit 13, the first punch 17 and thefirst die 20 are relatively moved in the vertical direction, whereby aregion at which the blanked body 15A is to be blanked in the sheet W issubjected to half-blanking work.

Subsequently, the first punch 17 moves in a stroke up to the top deadcenter position, and movement further upward is stopped. At this time,the upper surface 17 a of the first punch 17 approaches the lowersurface 20 a of the first die 20 up to a position separated by adistance dimension, which is 45% of the thickness dimension d of thesheet W. Next, the first punch 17 moves to the bottom dead centerposition, after which movement is stopped. In other words, the firststage S1 in the first working unit 13 ends. Thereafter, pushing up ofthe sheet W by the sheet pushing portion is stopped, and the sheet Wmoves away from the first die 20. The sheet W is subsequently passedfrom the first working unit 13 into the second working unit 14. Notethat the half-blanked portion 15 in the present embodiment is subjectedto processing to achieve a certain radius by the inner-side edge portion20 b of the first die 20, and is therefore formed such that thedeformation 15 b on the upper surface Wa side thereof is larger thanthat in the case of the first embodiment. In addition, the first sidewall surface 15 sh of the half-blanked portion 15 formed by the firstworking unit is shaved by the first die 20, similar to the case of thefirst embodiment, and therefore formed into a sheared-surface shape.

Next, the second working unit 14 will be explained below based on FIGS.14 to 19.

In the second working unit 14, the second die 23 is fixedly attached onthe lower die 22, and the second punch 26, which has a pairedrelationship with the second die 23, is fixedly attached to the lowersurface side of the upper die 25. The second die 23, as FIG. 14 shows,is formed with the second die hole 24 that has a cross section with agenerally circular shape. The second die hole 24 has the diameterdimension D4 (e.g. 29.3 mm) that is set so as to be greater than thediameter dimension D1 of the first die hole 21 in the first die 20 by0.4 mm, for example. In addition, the diameter dimension D4 of thesecond die hole 24 is set so as to be slightly smaller than the diameterdimension d1 of the through hole P, and also set so as to besubstantially the same dimension as the diameter d3 of the blanked body15A (see FIG. 19) to be described later.

The second punch 26 is formed so as to have a generally cylindricalshape. The second punch 26 is structured so as to achieve a form whereinthe cross-sectional shape for the second punch 26 when cut in adirection orthogonal to the vertical direction is a similar andscaled-down version of the cross-sectional shape for the first punch 17when cut in a direction orthogonal to the vertical direction. Inaddition, the diameter dimension D3 of the second punch 26 is set so asto enable cutting (or shaving in the present embodiment) of a regionwhere a deformation Wd is formed on the sheet W, and also set so as tobe shorter than the diameter dimension of the second die hole 24 by 0.2mm, for example. In other words, the second punch 26 and the second die23 have a paired relationship, and the clearance (a width dimension ofthe clearance) C2 therebetween is set so as to be a positive clearance(C2=(D4−D3)/2>0). In the present embodiment, the second die 23 is formedsuch that the clearance C2 has a width dimension (e.g. 0.1 mm) that is2.5% of the thickness dimension d (e.g. 4 mm) of the sheet W.

Next, the second stage S2 performed by the second working unit 14 willbe explained below.

The sheet W on which the first working unit 13 formed the half-blankedportion 15 is passed into the second working unit 14, and thehalf-blanked portion 15 is disposed below the second punch 26. Followingthis, the second stage S2 is started. In other words, the second punch26, as FIG. 15 shows, moves in a downward stroke toward the sheet W (thehalf-blanked portion 15), and presses the half-blanked portion 15 of thesheet W downward. At this time, the end edge portion 26 b of the secondpunch 26 positionally corresponds to an edge portion (a deformation onthe upper side) that forms the cross-sectional arc shape of thehalf-blanked portion 15 of the sheet W. Accordingly, the second sidewall surface 15 sb of the half-blanked portion 15 is formed into afracture-surface shape, similar to the case of the first embodiment. Asthe second punch 26 presses the half-blanked portion 15 furtherdownward, as FIG. 16 shows, the first side wall surface 15 sh and thesecond side wall surface 15 sb of the half-blanked portion 15 connect,and result in the cutting of the half-blanked portion 15 from the sheetW.

Next, as FIG. 17 shows, the second punch 26 presses the half-blankedportion 15 further downward and the second die 23 starts to shear theside wall surface (the blanked surface) 15 a of the half-blanked portion15 (a region to become the blanked body 15A). In other words, the seconddie 23 blanks the half-blanked portion 15 that is pushed downward by thesecond punch 26 from the sheet W, and starts to perform shaving work onthe side wall surface 15 a of the half-blanked portion 15. As FIG. 18shows, further movement of the second punch 26 in the downward strokeresults in the progressive performance of shaving work on the side wallsurface 15 a of the half-blanked portion 15.

At this point in time, the half-blanked portion 15 is still in a fittedstate inside the through hole P of the sheet W. However, with thefurther performance of shaving work on the side wall surface Pa by thesecond die 23, as FIG. 19 shows, the half-blanked portion 15 is pushedout of the through hole P by the second punch 26 and blanked from thesheet W to become the blanked body 15A. A majority of the side wallsurface 15 a of the blanked body 15A is formed into a sheared-surfaceshape due to shaving work performed by the second die 23. Note that aportion among the side wall surface 15 a of the blanked body 15A that isnot formed into a sheared-surface shape is a region of the half-blankedportion 15 (the blanked body 15A) that will ultimately be cut from thesheet W by pressure from the second punch 26, and is formed into afracture-surface shape. In addition, scraps (shaving scraps) generateddue to the second die 23 performing shaving work on the side wallsurface 15 a adhere to the sheet W. Therefore, the side wall surface Pais formed into a fracture-surface shape.

In addition to the effects (3) to (5), (8), and (9) of the firstembodiment, the further effects specified below can be obtained in thepresent embodiment.

(10) If, for instance, the clearance C1 between the first punch 17 andthe first die 20 (the first die hole 21) is set as a positive clearance,then tensile stress acts on a portion of the sheet W sandwiched betweenthe first punch 17 and the second die 20. Therefore, when the firstpunch 17 pushes the sheet W upward in the first working unit 13, thepushed region may fracture and form a fracture surface on the sheet W.However, in the present embodiment, the clearance C1 is a negativeclearance, and therefore compression stress acting on the portion of thesheet W sandwiched between the first punch 17 and the second die 20suppresses fractures. As a consequence, it is possible to suppress theformation of a fracture surface on the sheet W in the first working unit13. Furthermore, in the second working unit 14, when the sheet W issubjected to blanking work, the second die 23 performs shaving work onthe side wall surface 15 a of the half-blanked portion 15 (the blankedbody 15A). Moreover, since the clearance C2 between the second punch 26and the second die 23 is a positive clearance, it is possible to avoidcontact between the second punch 26 and the second die 23. Accordingly,an increase in the size of the apparatus itself and an increase in thenumber of processes for performing blanking work on the sheet W can besuppressed. And at the same time, it is possible to form into asheared-surface shape the side wall surface 15 a of the blanked body 15Ablanked from the sheet W, and also possible to suppress the generationof burrs on the blanked body 15A.

(11) In the first working unit 13, the half-blanked portion 15 is formedat a region where the through hole P is to be formed (a region to beblanked) in the sheet W; and in the second working unit 14, theperiphery of the half-blanked portion 15 is subjected to blanking work.Therefore, shaving scraps generated when the side wall surface 15 a ofthe blanked body 15A is subjected to shaving work in the second workingunit 14 can be made to adhere to the sheet W, which is not used as aproduct. Moreover, adhering of the shaving scraps to the second punch 26can be suppressed.

(12) If, for instance, the clearance (the width dimension of thepositive clearance) C2 is set to a width dimension that is less than0.3% of the thickness dimension d of the sheet W, then there is the riskof an increased load acting on the second punch 26 and the second die 23when the half-blanked portion 15 is blanked from the sheet W by thesecond punch 26. In other words, there is a possibility of shorteningthe lives of the second punch 26 and the second die 23. On the otherhand, if the clearance C2 is set to a width dimension that is greaterthan 8.0% of the thickness dimension d of the sheet W, then when thesecond punch 26 and the second die 23 punch the blanked body 15A fromthe sheet W, burrs may be generated on the blanked body 15A. However, inthe present embodiment, the clearance C2 is set to a width dimensionthat is 2.5% of the thickness dimension d of the sheet W. Accordingly,the lives of the second punch 26 and the second die 23 can belengthened, and the generation of burrs on the blanked body 15A when theblanked body 15A is blanked from the sheet W by the second punch 26 andthe second die 23 can be satisfactorily suppressed.

(13) If, for instance, the difference between the diameter dimension D4of the second die hole 24 of the second die 23 and the diameterdimension D1 of the first die hole 21 of the first die 20 is set shorterthan 0.02 mm, then a problem such as the following may occur. Namely,the width dimension of the connecting region that connects thehalf-blanked portion 15 and the sheet W becomes excessively small (thewidth of a certain shaving amount becomes excessively narrow) comparedto that in the present embodiment. Therefore, there is a risk thatperforming shaving work on the side wall surface 15 a of the blankedbody 15A will become difficult in the second stage S2. On the otherhand, if the difference between the diameter dimension D4 of the seconddie hole 24 of the second die 23 and the diameter dimension D1 of thefirst die hole 21 of the first die 20 is set greater than 0.6 mm, then aproblem such as the following may occur. Namely, when the second punch26 and the second die 23 punch the blanked body 15A from the sheet W inthe second stage S2, the inner-side edge portion of the second die 23shears a region on the inner peripheral side of the half-blanked portion15 formed in the first stage S1, whereby the load acting on the seconddie 23 increases compared to that in the case of the present embodiment.However, in the present embodiment, the second die 23 is formed suchthat the difference between the diameter dimension D4 of the second diehole 24 thereof and the diameter dimension D1 of the first die hole 21of the first die 20 is 0.4 mm. Therefore, the width of a certain shavingamount in the second stage S2 can be satisfactorily ensured, and thelife of the second die 23 can be further lengthened.

(14) If, for instance, when the first die 20 is cut in the verticaldirection, the curved surface 20 c of the inner-side edge portion 20 bof the first die 20 is formed into an arc shape whose curvature radiusis greater than a curvature radius with a length dimension that is 7.5%of the thickness dimension d of the sheet W, then a problem such as thefollowing may occur. Namely, when the sheet W is subjected tohalf-blanking work in the first stage S1, there is a risk of forming anexcessively large deformation on the upper side of the sheet W. However,in the present embodiment, the curved surface 17 c of the end edgeportion 17 b of the first punch 17 is formed so as to have a curvatureradius that is 7.5% of the thickness dimension d of the sheet W.Therefore, the deformation Wc formed on the sheet W can besatisfactorily suppressed so as not to become excessively large.

Third Embodiment

Next, a third embodiment according to the present invention will beexplained based on FIG. 20. Note that the third embodiment differssomewhat from the first embodiment with respect to the working units.Thus, the following explanation will mainly describe portions differingfrom the first embodiment; like symbols are used for members andstructures that are identical to or correspond to those in the firstembodiment, and redundant explanations shall be omitted.

The press working apparatus 11 according to the present embodiment hasthe first working unit 13 and the second working unit 14. The pressworking apparatus 11 is designed to form the through hole P with apredetermined shape (whose cross section is a generally circular shapein the present embodiment) in the sheet W, which is formed from ametallic material (e.g. hot-rolled sheet steel (JIS SAPH370) forautomobile structures) with a predetermined thickness (e.g. 3 mm). Inthe first working unit 13, the first punch 17 is fixedly attached on thelower die 16, and the first die 20 corresponding to the first punch 17is fixedly attached on the lower surface side of the upper die 19. Thefirst punch 17 is formed so as to have a generally cylindrical shape,and also formed such that the diameter dimension D2 thereof is 20.2 mm,for example.

In addition, the first die 20 is formed with the first die hole 21 thathas a cross section with a generally circular shape. The negativeclearance C1 between the first die 20 and the first punch 17 is set soas to have a width dimension (e.g. 0.3 mm) that is 10% of the thicknessdimension d (e.g. 3 mm) of the sheet W. Namely, the first die hole 21 ofthe first die 20 is set such that the diameter dimension D1 thereof is19.6 mm, for example. Note that in the present embodiment, the end edgeportion 17 b on the upper surface 17 a side (a side facing the sheet W)of the first punch 17 and the inner-side edge portion 20 b on the lowersurface 20 a side (a side facing the sheet W) of the first die 20 arenot subjected to processing that would form curved surfaces thereon witha certain radius.

Next, the first stage S1 performed by the first working unit 13 will beexplained below.

A region to be blanked on the sheet W is disposed in an area over thefirst punch 17. At such time, the sheet pushing portion pushes the sheetW upward (toward the first die 20 side), and puts the upper surface Waof the sheet W in contact with the lower surface 20 a of the first die20. Next, the first punch 17 moves upward from the bottom dead centerposition in a stroke according to driving of the hydraulic cylinder.Thus, the sheet W is formed with the half-blanked portion 15, which hasa shape that projects toward the first die 20 side (upward).Accordingly, in the first working unit 13, the first punch 17 and thefirst die 20 are relatively moved in the vertical direction, whereby aregion at which the blanked body 15A is to be blanked in the sheet W issubjected to half-blanking work. Furthermore, at this time, a region ofthe sheet W in contact with the end edge portion 17 b of the first punch17 is formed into a sheared-surface shape as a result of shaving workperformed by the first punch 17.

Subsequently, the first punch 17 moves in a stroke up to the top deadcenter position, and movement further upward is stopped. At this time,the upper surface 17 a of the first punch 17 approaches the lowersurface 20 a of the first die 20 up to a position separated by adistance dimension, which is 33% of the thickness dimension d of thesheet W. Next, the first punch 17 moves to the bottom dead centerposition, after which movement is stopped. In other words, the firststage S1 in the first working unit 13 ends. Thereafter, pushing up ofthe sheet W by the sheet pushing portion is stopped, and the sheet Wmoves away from the first die 20. The sheet W is subsequently passedfrom the first working unit 13 into the second working unit 14.

Next, the second working unit 14 will be explained below.

In the second working unit 14, the second die 23 is fixedly attached onthe lower die 22, and the second punch 26, which has a pairedrelationship with the second die 23, is fixedly attached to the lowersurface side of the upper die 25. The second die 23 is formed with thesecond die hole 24 that has a cross section with a generally circularshape. The second die hole 24 has the diameter dimension D4 (e.g. 20.5mm) that is set so as to be greater than the diameter dimension D1 ofthe first die hole 21 in the first die 20 by 0.3 mm, for example.

The second punch 26 is formed so as to have a generally cylindricalshape. The second punch 26 is structured so as to achieve a form whereinthe cross-sectional shape for the second punch 26 when cut in adirection orthogonal to the vertical direction is a similar and enlargedversion of the cross-sectional shape for the first punch 17 when cut ina direction orthogonal to the vertical direction. In addition, thesecond punch 26 is formed such that the diameter dimension D3 thereof isset greater than the diameter dimension D1 of the first die hole 21 ofthe first die 20 by 0.5 mm. In other words, the diameter dimension D3 ofthe second punch 26 is set so as to be 20.1 mm, for example. Therefore,the diameter dimension D3 of the second punch 26 is shorter than thediameter dimension D4 of the second die hole 24 by 0.4 mm, for example.Accordingly, the second punch 26 and the second die 23 have a pairedrelationship, and the clearance (a width dimension of the clearance) C2formed therebetween is set so as to be a positive clearance(C2=(D4−D3)/2>0). In the present embodiment, the second die 23 is formedsuch that the clearance C2 has a width dimension (e.g. 0.2 mm) that is6.7% of the thickness dimension d (e.g. 3 mm) of the sheet W.

Next, the second stage S2 performed by the second working unit 14 willbe explained below.

The sheet W on which the first working unit 13 formed the half-blankedportion 15 is passed into the second working unit 14, and thehalf-blanked portion 15 is disposed below the second punch 26. Followingthis, the second stage S2 is started. In other words, the second punch26 moves in a downward stroke toward the sheet W (the half-blankedportion 15), and presses the half-blanked portion 15 of the sheet Wdownward. Accordingly, the second side wall surface 15 sb of thehalf-blanked portion 15 is formed into a fracture-surface shape. As thesecond punch 26 presses the half-blanked portion 15 further downward,the first side wall surface 15 sh and the second side wall surface 15 sbof the half-blanked portion 15 connect, and result in the cutting of thehalf-blanked portion 15 from the sheet W.

Next, the second punch 26 presses the half-blanked portion 15 furtherdownward, whereby the second punch 26 starts to perform shaving work onthe side wall surface Pa of the through hole P. In this case, thediameter dimension D3 of the second punch 26 is smaller than thediameter dimension D3 of the first punch 17 by 0.1 mm. Therefore, asFIG. 20 shows, a region (an upper-side region in FIG. 20) P1 sheared bythe second punch 26 is formed such that a diameter dimension thereof(e.g. 20.1 mm) is smaller than a diameter dimension (e.g. 20.2 mm) of aregion (a lower-side region in FIG. 20) P2 sheared by the first punch17. Thus, the through hole P formed in the sheet W by the press workingapparatus 11 according to the present embodiment is formed with theupper-side region P1 and the lower-side region P2, which has a diameterdimension that is greater than the diameter dimension of the upper-sideregion P1.

In addition to the effects (1) to (5), (8), and (9) of the firstembodiment, the further effect specified below can be obtained in thepresent embodiment.

(15) If, for instance, the difference between the diameter dimension D3of the second punch 26 and the diameter dimension D1 of the first diehole 21 of the first die 20 is set smaller than 0.02 mm, then a problemsuch as the following may occur. Namely, the width dimension of theconnecting region that connects the half-blanked portion 15 and thesheet W becomes excessively small (the width of a certain shaving amountbecomes excessively narrow) compared to that in the present embodiment.Therefore, there is a risk that performing shaving work on the side wallsurface Pa of the upper-side region P1 of the through hole P will becomedifficult in the second stage S2. On the other hand, if the differencebetween the diameter dimension D3 of the second punch 26 and thediameter dimension D1 of the first die hole 21 of the first die 20 isset greater than 0.6 mm, then a problem such as the following may occur.Namely, when the second punch 26 and the second die 23 punch the blankedbody 15A from the sheet W in the second stage S2, the load acting on theend edge portion 26 b of the second punch 26 increases. However, in thepresent embodiment, the second punch 26 is formed such that thedifference between the diameter dimension D4 thereof and the diameterdimension D1 of the first die hole 21 of the first die 20 is 0.5 mm.Therefore, the width of a certain shaving amount in the second stage S2can be satisfactorily ensured, and the life of the second punch 26 canbe further lengthened.

Note that the respective embodiments above may be modified to achieveother embodiments (other examples) such as the following.

In the first embodiment, provided that the curvature radius of thecurved surface 17 c is a curvature radius that is equal to or less than7.5% of the thickness dimension d of the sheet W, the end edge portion17 b of the first punch 17 may be formed such that the curved surface 17c has an arbitrary curvature radius (e.g. a curvature radius that is1.5% of the thickness dimension d).

In the first embodiment, the inner-side edge portion 20 b of the firstdie 20 may be formed such that the shape of a vertical cross sectionthereof forms a part of the circular shape of an arbitrary diameterdimension that is equal to or less than a diameter dimension that is15.0% of the thickness dimension d of the sheet W (e.g. a diameterdimension that is 10% of the thickness dimension d). In addition, theend edge portion 26 b of the second punch 26 may be formed such that theshape of a vertical cross section thereof forms a part of the circularshape of an arbitrary diameter dimension that is equal to or less than adiameter dimension that is 15.0% of the thickness dimension d of thesheet W (e.g. a diameter dimension that is 5% of the thickness dimensiond).

In the second embodiment, provided that the curvature radius of thecurved surface 20 c is a curvature radius that is equal to or less than7.5% of the thickness dimension d of the sheet W, the inner-side edgeportion 20 b of the first die 20 may be formed such that the curvedsurface 20 c has an arbitrary radius (e.g. a curvature radius that is 6%of the thickness dimension d).

In the second embodiment, the end edge portion 17 b of the first punch17 may be formed such that the shape of a vertical cross section thereofforms a part of the circular shape of an arbitrary diameter dimensionthat is equal to or less than a diameter dimension that is 15.0% of thethickness dimension d of the sheet W (e.g. a diameter dimension that is5% of the thickness dimension d). In addition, the end edge portion 26 bof the second punch 26 may be formed such that the shape of a verticalcross section thereof forms a part of the circular shape of an arbitrarydiameter dimension that is equal to or less than a diameter dimensionthat is 15.0% of the thickness dimension d of the sheet W (e.g. adiameter dimension that is 5% of the thickness dimension d).

In the third embodiment, the end edge portion 17 b of the first punch 17may be formed such that the shape of a vertical cross section thereofforms a part of the circular shape of an arbitrary diameter dimensionthat is equal to or less than a diameter dimension that is 15.0% of thethickness dimension d of the sheet W (e.g. a diameter dimension that is5% of the thickness dimension d). In addition, the inner-side edgeportion 20 b of the first die 20 may be formed such that the shape of avertical cross section thereof forms a part of the circular shape of anarbitrary diameter dimension that is equal to or less than a diameterdimension that is 15.0% of the thickness dimension d of the sheet W(e.g. a diameter dimension that is 10% of the thickness dimension d).Furthermore, the end edge portion 26 b of the second punch 26 may beformed such that the shape of a vertical cross section thereof forms apart of the circular shape of an arbitrary diameter dimension that isequal to or less than a diameter dimension that is 15.0% of thethickness dimension d of the sheet W (e.g. a diameter dimension that is5% of the thickness dimension d). Moreover, the end edge portion 26 b ofthe second punch 26 may be formed such that the shape of a verticalcross section thereof forms a part of the circular shape of an arbitrarydiameter dimension that is equal to or less than a diameter dimensionthat is 15.0% of the thickness dimension d of the sheet W (e.g. adiameter dimension that is 5% of the thickness dimension d).

In the first embodiment, provided that the difference between thediameter dimension D3 of the second punch 26 and the diameter dimensionD2 of the first punch 17 is within a range of 0.02 mm to 0.6 mm, thesecond punch 26 may be formed such that the difference between thediameter dimension D3 and the diameter dimension D2 is an arbitrarydiameter dimension (e.g. 0.1 mm).

In the first embodiment, the first punch 17 and the second punch 26 maybe respectively structured such that the shapes of the respective crosssections, when cut in a direction orthogonal to the vertical direction,are arbitrary cross-sectional shapes that correspond to thecross-sectional shape (the hole shape) of the through hole P formed inthe sheet W. However, the cross-sectional shape of the second punch 26is preferably a shape that is a generally similar and enlarged versionof the cross-sectional shape of the first punch 17.

In other words, the first punch 17 and the second punch 26 mayrespectively have cross-sectional shapes that are formed as generallysquare shapes. Here, as FIG. 21 shows, a cross section (hereinafterreferred to as a “first punch cross section”) 17A of the first punch 17is superimposed in a frame format in the vertical direction on a crosssection (hereinafter referred to as a “second punch cross section”) 26Aof the second punch 26. In such case, a distance dimension da betweenadjacent outer peripheral regions 17 d, 26 d that have mutually similarshapes may be set to an arbitrary distance dimension (e.g. 0.15 mm),provided that the distance dimension is within a range of 0.01 mm to 0.3mm. In this case, the distance dimension da is, respectively, thedistance dimension between a top side of the first punch cross section17A and a top side of the second punch cross section 26A; and thedistance dimension between the right side of the first punch crosssection 17A and the second punch cross section 26A. Likewise, thedistance dimension da also is, respectively, the distance dimensionbetween the bottom side of the first punch cross section 17A and thebottom side of the second punch cross section 26A; and the distancedimension between the left side of the first punch cross section 17A andthe left side of the second punch cross section 26A. Note that the top,bottom, left, and right as used here refer to the top, bottom, left, andright as shown in FIG. 21.

Also, the press working apparatus 11 according to the first embodiment,as FIGS. 22 and 23 show, may be used along with other processing devices(such as a press working apparatus having a punch and a die that differin shape and size from the punches 17, 26 and the dies 20, 23) to form acarrier 40. Note that the carrier 40 is a type of press-formed part foran automatic transmission.

Also, in the second embodiment as well, the first punch 17 and thesecond punch 26 may be respectively structured such that the shapes ofthe respective cross sections, when cut in a direction orthogonal to thevertical direction, are arbitrary cross-sectional shapes (e.g. crosssections with polygonal shapes) that correspond to the cross-sectionalshape (the hole shape) of the through hole P formed in the sheet W. Inother words, the press working apparatus 11 according to the secondembodiment, as FIG. 24 shows, may be used to form a backing plate 36that is formed with a plurality of projections 35 on an outer-sidesurface (a side wall surface 15A) side thereof. In this case, the holeshape of the second die hole 24 of the second die 23 is preferably ashape that is a generally similar and scaled-down version of the holeshape of the first die hole 21 of the first die 20.

-   -   Furthermore, in the third embodiment as well, the first punch 17        and the second punch 26 may be respectively structured such that        the shapes of the respective cross sections, when cut in a        direction orthogonal to the vertical direction, are arbitrary        cross-sectional shapes (e.g. cross sections with polygonal        shapes) that correspond to the cross-sectional shape (the hole        shape) of the through hole P formed in the sheet W. In this        case, the cross-sectional shape of the second punch 26 is        preferably a shape that is a generally similar and enlarged        version of the hole shape of the first die hole 21 of the first        die 20.

In the respective embodiments above, provided that the width dimensionis within a range of 0.3% to 8% of the thickness dimension d of thesheet W, the second punch 26 may be formed such that the clearance C2has an arbitrary width dimension (e.g. a width dimension that is 1% ofthe thickness dimension d).

In the respective embodiments above, provided that the width dimensionis within a range of 1% to 15% of the thickness dimension d of the sheetW, the first punch 17 may be formed such that the clearance C 1 has anarbitrary width dimension (e.g. a width dimension that is 3.0% of thethickness dimension d).

In the second embodiment, the second die 23 may be structured such thatthe distance dimension between an inner peripheral region of the crosssection of the second die 23 and an inner peripheral region of the crosssection of the first die 20 is an arbitrary distance dimension (e.g. 3mm) within a range of 0.01 mm to 0.3 mm. For such a structure, in thesecond working unit 14, the second die 23 shears only a portion of theside wall surface 15 a of the blanked body 15A. Namely, the blanked body15A has a major diameter portion whose diameter dimension is large and aminor diameter portion whose diameter dimension is smaller than themajor diameter portion, which are provided connected in the verticaldirection.

In the respective embodiments above, when the sheet W is half-blanked inthe first working unit 13, the distance dimension d2 in the verticaldirection between the upper surface 17 a of the first punch 17 and thelower surface 20 a of the first die 20 may be set to an arbitrarydistance dimension, provided that the distance dimension is within arange of 10% to 50% of the thickness dimension d. For example, thedistance dimension d2 may be set to a distance dimension that is 40% ofthe thickness dimension d.

In the first embodiment, as FIGS. 25A, 25B, and 25C show, the pressworking apparatus 11 may be realized by a press working apparatus thatforms a notched portion 31 on a sheet 30. Namely, in the first stage S1,a half-blanked portion 32 is formed at a region formed with the notchedportion 31 in the sheet 30. Then, in the second stage S2, thehalf-blanked portion 32 of the sheet 30 is subjected to blanking work,and a side wall surface 31 a of the notched portion 31 is subjected toshaving work. As a consequence, the sheet 30 is formed with the notchedportion 31 having the side wall surface 31 a, which has been processedinto a sheared-surface shape.

In the respective embodiments above, the press working apparatus 11 mayhave a structure in which the first punch 17 is fixedly attached to thelower surface side of the upper die 19 in the first working unit 13, andthe second punch 26 is fixedly attached to the upper surface side of thelower die 22 in the second working unit 14. For such a case, in thefirst stage S1, as FIG. 25A shows, the half-blanked portion 32 is formedhaving a shape that projects downward from the sheet 30.

In the respective embodiments above, the press working apparatus 11 mayhave a structure in which the first punch 17 is fixedly attached to thelower surface side of the upper die 19 in the first working unit 13, andthe second punch 26 is fixedly attached to the lower surface side of theupper die 25 in the second working unit 14. In the case of such astructure, the sheet 30 formed with the half-blanked portion 32 by thefirst stage S1 of the first working unit 13 may be turned over such thata concave portion of the half-blanked portion 32 faces upward, afterwhich the sheet 30 is passed into the second working unit 14.

In the respective embodiments above, the press working apparatus 11 maybe realized as an apparatus that forms an arbitrary press-formed part,provided that it is a press-formed part for an automatic transmission.In addition, the press working apparatus 11 may be realized as anapparatus that forms an element of a belt for a continuously variabletransmission. Namely, the press working apparatus 11 may be an apparatusthat forms an arbitrary press-formed part, provided that it is a partthat has a relative thickness and is not a thin plate.

1. A press working apparatus, which performs blanking work on a sheet,comprising: a first working unit having a first upper die and a firstlower die, wherein at least one of the first upper die and the firstlower die is mobile in the vertical direction with respect to the other,with the first upper die fixedly attached with at least one among anopposing first punch and a first die, and the first lower die fixedlyattached with the other among the first punch and the first die, and anegative clearance is set between the first punch and the first die asviewed from the vertical direction, and half-blanking work is performedon the sheet by relatively moving the first punch and the first die inthe vertical direction; and a second working unit having a second upperdie and a second lower die, wherein at least one of the second upper dieand the second lower die is mobile in the vertical direction withrespect to the other, with the second upper die fixedly attached with atleast one among a second punch and a second die having a pairedrelationship, and the second lower die fixedly attached with the otheramong the second punch and the second die, and a positive clearance isset between the second punch and the second die as viewed from thevertical direction, and when a half-blanked portion that was formed inthe sheet by half-blanking work performed by the first working unit isblanked to become a blanked body by the second punch, a blanked surfaceis formed along a blanking direction on a region where the blanked bodyis blanked from the sheet, and at least a portion of the blanked surfaceis subjected to shaving work performed by the second punch.
 2. The pressworking apparatus according to claim 1, wherein the second punch isstructured so as to achieve a form wherein a cross-sectional shape forthe second punch when cut in a direction orthogonal to the verticaldirection is a similar and enlarged version of a cross-sectional shapefor the first punch when cut in a direction orthogonal to the verticaldirection.
 3. The press working apparatus according to claim 2, whereinthe second punch is structured such that if the cross-sectional shapefor the second punch when cut in a direction orthogonal to the verticaldirection overlaps in the vertical direction with the cross-sectionalshape for the first punch when cut in a direction orthogonal to thevertical direction, then there is a distance dimension of 0.01 mm to 0.3mm between adjacent outer peripheral regions with mutually similarshapes.
 4. The press working apparatus according to any one of claims 1to 3, wherein the first die is formed with a through hole runningtherethrough that extends in the vertical direction, and the secondpunch is structured such that the cross-sectional shape for the secondpunch when cut in a direction orthogonal to the vertical direction is asimilar and enlarged shape of a hole shape of the through hole when thefirst die when is cut in a direction orthogonal to the verticaldirection.
 5. The press working apparatus according to claim 4, whereinthe second punch is structured such that if the cross-sectional shapefor the second punch when cut in a direction orthogonal to the verticaldirection overlaps in the vertical direction with the cross-sectionalshape for the first die when cut in a direction orthogonal to thevertical direction, then there is a distance dimension of 0.01 mm to 0.3mm between an outer peripheral region of the cross section of the secondpunch and an inner peripheral region of the cross section of the firstdie, which have a mutually similar relationship.
 6. A press workingapparatus, which performs blanking work on a sheet, comprising: a firstworking unit having a first upper die and a first lower die, wherein atleast one of the first upper die and the first lower die is mobile inthe vertical direction with respect to the other, with the first upperdie fixedly attached with at least one among an opposing first punch anda first die, and the first lower die fixedly attached with the otheramong the first punch and the first die, and a negative clearance is setbetween the first punch and the first die as viewed from the verticaldirection, and half-blanking work is performed on the sheet byrelatively moving the first punch and the first die in the verticaldirection; and a second working unit having a second upper die and asecond lower die, wherein at least one of the second upper die and thesecond lower die is mobile in the vertical direction with respect to theother, with the second upper die fixedly attached with at least oneamong a second punch and a second die having a paired relationship, andthe second lower die fixedly attached with the other among the secondpunch and the second die, and a positive clearance is set between thesecond punch and the second die as viewed from the vertical direction,and when a half-blanked portion that was formed in the sheet byhalf-blanking work performed by the first working unit is blanked tobecome a blanked body by the second punch, a blanked surface is formedalong a blanking direction on the blanked body, and at least a portionof the blanked surface is subjected to shaving work performed by thesecond die.
 7. The press working apparatus according to claim 6, whereinthe first die and the second die are respectively formed with insertionholes running therethrough in the vertical direction, and the second dieis structured so as to achieve a form wherein a hole shape of theinsertion hole when the second die is cut in a direction orthogonal tothe vertical direction is a similar and scaled-down version of a holeshape of the insertion hole when the first die is cut in a directionorthogonal to the vertical direction.
 8. The press working apparatusaccording to claim 7, wherein the second die is structured such that ifa cross-sectional shape for the second die when cut in a directionorthogonal to the vertical direction overlaps in the vertical directionwith a cross-sectional shape for the first die when cut in a directionorthogonal to the vertical direction, then there is a distance dimensionof 0.01 mm to 0.3 mm between an outer peripheral region of a crosssection of the second die and an inner peripheral region of a crosssection of the first die, which have a mutually similar relationship. 9.The press working apparatus according to any one of claims 1 to 8,wherein the first working unit is structured such that if the firstpunch is made to relatively approach the first die, then the first punchis made to approach up to a position that is separated only by adistance dimension that is 10% to 50% of a thickness dimension of thesheet.
 10. The press working apparatus according to any one of claims 1to 9, wherein the first punch is formed such that a width dimension ofthe negative clearance is a width dimension that is 1% to 15% of thethickness dimension of the sheet.
 11. The press working apparatusaccording to any one of claims 1 to 10, wherein the second punch isfixedly attached with the second lower die if the first punch is fixedlyattached with the first upper die, and the second punch is fixedlyattached with the second upper die if the first punch is fixedlyattached with the first lower die.
 12. The press working apparatusaccording to any one of claims 1 to 11, wherein the second punch isformed such that a width dimension of the positive clearance is a widthdimension that is 0.3% to 8% of the thickness dimension of the sheet.13. The press working apparatus according to any one of claims 1 to 12,wherein at least one among an end edge portion on a side facing thesheet in the first punch and an inner-side edge portion on a side facingthe sheet in the first die is subjected to chamfering work so as to havea curved surface.
 14. The press working apparatus according to claim 13,wherein the curved surface formed on at least one among the end edgeportion on a side facing the sheet in the first punch and the inner-sideedge portion on a side facing the sheet in the first die is formed so asto achieve an arc shape, which has a curvature radius with a lengthdimension that is equal to or less than 7.5% of the thickness dimensionof the sheet when the first punch and the first die are cut in thevertical direction.
 15. The press working apparatus according to any oneof claims 1 to 14, wherein an end edge portion on a side facing thesheet in the second punch is subjected to chamfering work so as to havea curved surface.
 16. The press working apparatus according to claim 15,wherein the curved surface of the end edge portion on a side facing thesheet in the second punch is formed so as to achieve an arc shape, whichhas a curvature radius with a length dimension that is equal to or lessthan 7.5% of the thickness dimension of the sheet when the second punchis cut in the vertical direction.
 17. A blanked product manufactured byblanking a blanked body from a sheet using a press working apparatusaccording to any one of claims 1 to
 16. 18. A press working method,which performs blanking work on a sheet, comprising: a first stage wherea first punch and a first die in a paired relationship are used toperform half-blanking work on a region where a blanked body is to beblanked in the sheet; and a second stage where a second punch and asecond die in a paired relationship are used to blank the blanked bodyfrom the region in the sheet subjected to half-blanking in the firststage, and at such time, the second punch performs shaving work on atleast a portion of a blanked surface along a blanking direction on aregion where the blanked body is blanked.
 19. A press working method,which performs blanking work on a sheet, comprising: a first stage wherea first punch and a first die in a paired relationship are used toperform half-blanking work on a region where a blanked body is to beblanked in the sheet; and a second stage where a second punch and asecond die in a paired relationship are used to blank the blanked bodyfrom the region in the sheet subjected to half-blanking in the firststage, and at such time, the second die performs shaving work on atleast a portion of a blanked surface along a blanking direction on theblanked body.